1. Field of the Invention
The present invention relates to a connector for tubing. In particular, but not exclusively, the present invention relates to the sealing of a connector for expandable downhole tubing sections.
2. Description of the Related Art
In the oil and gas exploration and production industry, expandable tubing has been developed and has a variety of uses. These include expandable borehole casing and liner, and expandable sand exclusion based tubing assemblies or sandscreens, such as that disclosed in International patent publication no WO97/17524 (Shell), and as sold under the ESS Trademark by the present applicant.
Expandable tubing offers a number of advantages over conventional borehole tubing, as the expandable tubing can be run into a borehole in an unexpanded state and subsequently expanded downhole. This allows the tubing to be run through existing tubing and then expanded to a larger diameter within the borehole.
The expandable tubing sections typically include a male threaded portion (pin) and a female threaded portion (box) at opposite ends, for joining adjacent sections of tubing together end to end. The pin and box of adjacent tubing sections thus form connectors for coupling the tubing sections together. A proposed connector assembly for expandable tubing is disclosed in the Applicant's U.S. Pat. No. 5,924,745, the disclosure of which is incorporated herein by way of reference.
Maintaining a seal between the pin and box portions post expansion can be problematic due to elastic recovery, which tends to cause the pin to draw inwardly out of contact with the box.
The Applicant's International patent publication No. WO02/075107 discloses a method of forming a seal between two tubular members by providing a first tubular member having a recess with a sealing member located in the recess, and by expanding the first tubular member such that the sealing member engages an inner surface of a second tubular member.
It is amongst the objects of embodiments of the present invention to obviate or mitigate the foregoing disadvantage.